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Question 1

What is an evaporator feed control?

Answer 1

An evaporator feed control is a refrigerant flow control attached to the entrance of an evaporator in a refrigeration system

Question 2

What are two types of fixed evaporator feed controls?

Answer 2

Fixed Orifice
Tube with fixed length

Question 3

List 6 types of adjustable evaporator feed controls.

Answer 3

Hand expansion valve
Thermostatic expansion valve (TEV or TXV)
Automatic Expansion valve (AEV)
Electronic Expansion Valve (EEV)
Low Side Float (LSF)
High Side Float (HSF)

Question 4

State the basic operating principle of evaporator feed controls

Answer 4

Manage the rate of refrigerant flow into the evaporator

Question 5

What is a British thermal unit (BTU)

Answer 5

The amount of heat required to raise or lower the temperature of 1 lb of distilled water at sea level 1 degree Fahrenheit

Question 6

What is a gas charge

Answer 6

The pressure producing part of a thermal bulb that does not contain liquid refrigerant

Question 7

What is a flooded evaporator

Answer 7

An evaporator that contains liquid refrigerant at all times

Question 8

What is a direct expansion evaporator

Answer 8

An evaporator in which the liquid refrigerant expands rapidly to a gaseous state as it leaves the outlet of the metering device and enters the inlet of the evaporator

Question 9

What is an external equalizer

Answer 9

A tube connected to the control section of an expansion valve and to the outlet of an evap at the same time

Question 10

Define Liquid charge

Answer 10

A liquid charge is the pressure producing part of a thermal bulb that contains liquid which has some vapour

Question 11

What is the refrigeration effect

Answer 11

The refrigeration effect is the moving of heat from a place where heat is not wanted to a place where the heat is wanted

Question 12

What is a fixed orifice metering device

Answer 12

A restrictor that drastically reduces the pressure and flow of liquid refrigerant through a relatively short and confined space

Question 13

4 considerations in the selection of a fixed orifice

Answer 13

1. Capacity of the system
2. Length of line set from the condensing unit to the evaporator
3. equivalent feet of line set due to vertical lift in the liquid line
4. type of refrigerant used in the system

Question 14

What is a capillary tube metering device

Answer 14

it is a metering device that is a long tube usually made from copper, with a small internal diameter

Question 15

What is a TXV

Answer 15

A thermostatic expansion valve is a metering device that regulates liquid refrigerant flow into an evaporator based on the amount of superheated vapour at that evaporators outlet

Question 16

6 Considerations when choosing a TXV

Answer 16

Liquid temperature entering the valve
Pressure drop across the valve
capacity of the system
externally or internally equalized valve
body type and connections
thermostatic bulb and element charge

Question 17

Which two types of refrigerant metering devices do you use for a flooded evaporator

Answer 17

1. Low side float, hand expansion valve
2. high side float

Question 18

State 2 functions that the filter drier performs in relation to the metering device

Answer 18

1. they trap particles that may plug up metering device inlets
2. they remove water from the refrigerant

Question 19

List 5 types of refrigeration effect

Answer 19

1. metering a solid
2. immersing in a fluid
3. evaporating a liquid
4. thermoelectric
5. chemical reaction